The present invention is directed to a stationary impact attenuation system, and more specifically to a form of stationary impact attenuation system which is particularly suited for use at narrow hazard sites, such as at the ends of edge-of-road and median barriers, bridge pillars and center piers, for purposes of reducing the severity of vehicular collisions, especially of the kind involving fast moving motor vehicles and stationary objects, in an effort to thereby limit the extent of injury suffered by people as a consequence of such vehicular collisions as well as the damage done as a consequence of such vehicular collisions to the vehicles and the objects struck thereby.
It has long been known in the prior art to employ accident preventative measures in an effort to prevent and/or reduce the damage incurred by both humans and property resulting from vehicular collisions occurring on the Nation's major highways as well as its local roads. Such accident preventative measures may be classified for purposes of this discussion into two basic categories; namely, warning devices designed to be operative to forestall the occurrence of a vehicular collision, and protective devices designed to afford protection to both persons and property in the event of the ocurrence of a vehicular collision.
By way of exemplification and not limitation, the category of warning devices is intended to include such items as conventional traffic signs and traffic signals, emergency signs and signals displayed to warn of the temporary existence of a dangerous situation, etc. Protective devices fall into two classes. In the first class are those devices embodied in a vehicle as part of the construction of the vehicle, irrespective of whether the latter are subsequently affixed in some manner to the exterior of the vehicle. Examples of protective devices, which fall within the first class, are such things as padded dashboards, seat belts, etc. In the second class are to be found such things as various types of safety barriers designed to afford protection in the event of a vehicular collision between a moving vehicle and another moving vehicle, or between a moving vehicle and an immovable object. The present invention relates to a protective device of the type falling within the second class thereof as defined hereinabove, and more specifically, to such a device which is designed to afford protection in the event of a collision between a moving vehicle and an immovable object.
That there exists along the Nation's major highways and along its local roads a potential for danger has long been known. In this regard, one such potential for danger which one often encounters while traveling along the Nation's major highways and its local roads is that of the hazardous conditions occasioned by the presence on such highways and roads of men and equipment engaged in highway and road maintenance and repair operations. Such personnel and equipment need to be protected from being struck by an errant moving vehicle. More specifically, what is needed to provide such protection is an energy absorbing barrier which is portable in nature.
Although a great deal of the focus of the prior art heretodate has been directed towards providing various kinds of stationary energy absorbing barriers, there is known to exist in the prior art at least two different types of portable energy absorbing barriers, the latter more commonly being viewed as comprising a system. One such portable energy absorbing system is in the form of a hydro-cell system and consists of five rows of thirteen polyvinyl chloride plastic cells enveloped in a corset-like membrane. The entire unit is mounted on a metal platform, which is designed to be attached to the rear of a highway service vehicle. Each cell contains approximately three and one-half gallons of a water-calcium chloride solution. The latter solution functions to provide the system with the desired controlled crushing characteristics. The hydro-cell portable energy absorbing system, although being portable in nature and relatively easy to install, has been found to suffer from the major disadvantage that it cannot simultaneously satisfy the energy absorption and minimum stopping distance, i.e., deceleration requirements, for moving vehicles impacting thereagainst at speeds in excess of thirty miles per hour.
Another known form of portable energy abdorbing system is the modular crash cushion system, which is composed of thirty steel drums, i.e., ten rows with three drums per row. The thirty drums rest on a trailer, which is designed to be attached to a highway service vehicle at five points to provide the required degree of horizontal and vertical stability during impact. The principal disadvantage of the modular crash cushion portable energy system stems from the fact that it is nineteen and one-half feet long. As a consequence, because of the need to maintain a rigid interconnection between the trailer and the towing service vehicle at all times, this system has been shown to suffer from severe wear limitations as concerns both the trailer on which the drums rest and the service vehicle which tows the trailer. In addition, because of its relatively long length, this system has proven to be unsuitable for use on the hilly and curved sections of highways and roads, which are found to exist in many areas of the country.
Yet another example of a prior art form of portable energy absorbing system, and one that has found favor with those who have a need forsuch systems, is that which forms the subject matter of U.S. Pat. No. 4,200,310, which issued on Apr. 29, 1980 to the same inventor as that of the present application and which is assigned to the same assignee as the present application. As described therein, the portable energy absorbing system, which is operable as an impact attenuation device for reducing the severity of vehicular collisions, comprises guidance frame means, energy absorbing means and impacting plate means. The guidance frame means, which is operable to secure one end of the energy absorbing system in fixed relation to a vehicle, includes an attachment plate through which the guidance frame means is fastened at one end to the aforesaid vehicle, structural tubing members having one end thereof secured to theattachment plate, first support means operable for supporting the structural tubing members and for securing the other end of the structural tubing members to the aforesaid vehicle, and reinforcing means mounted on the structural tubing members operable to provide additional strength to the structural tubing members. The energy absorbing means, which functions to absorb the energy released during the vehicular collisions, includes a multiplicity of pipe sections connected together in series relation and supported in interposed relation between the guidance frame means and the impacting plate means. The impacting means, which is the portion of the energy absorbing system designed to be struck during the vehicular collisions, includes a reinforced plate means, structural members having one end thereof supported in sliding relation within the structural tubing members of the guidance frame means, and second support means having one end fastened to the aforesaid vehicle operable to provide additional vertical support to the energy absorbing system relative to the aforereferenced vehicle.
Continuing with the discussion of the second class of protective devices as the latter has been defined hereinbefore, the nature of the immovable objects which are being referred to herein are such things as bridge piers, light stanchions, guardrails, signposts, concrete walls and abutments, etc. Typically, an attempt is made to provide protection against a moving vehicle striking such immovable objects by positioning a stationary traffic safety barrier in proximity to the immovable object and so that it lies along the path, which the moving vehicle would most likely follow if it were to strike the immovable object. Such stationary traffic safety barriers are most often intended to function in the manner of an impact attenuation device; namely, to attenuate the forces produced as a result of the impact of the moving vehicle striking the immovable object and thereby reduce the severity of the vehicular collision as relates to the extent of injury suffered by the individuals riding in the moving vehicle and the amount of property damage incurred by both the moving vehicle and the immovable object.
For ease of reference during the following discussion, such stationary traffic safety barriers will hereinafter be referred to as stationary energy absorbing barriers. One of the earliest attempts made at providing a stationary energy absorbing barrier involved the employment of a system composed of fifty-five gallon drums. Patterns were cut into the lids of the drums to reduce the crushing strength of the system, i.e., to provide the system with the desired controlled crushing characteristics.
The successful implementation of this fifty-five gallon drum modular crash cushion system prompted a study of the feasibility of employing other possible forms of stationary energy absorbing barriers. In this regard, corrugated steel pipe was found to have favorable characteristics when it was statically crash tested. Moreover, the availability of corrugated steel pipe having a wide range of thickness and diameter dimensions made it feasible to employ a polymodular design in which the physical characteristics of the stationary energy absorbing barrier could be varied on a row to row basis.
Examples of other forms of stationary energy absorbing barriers, which are known to exist in the prior art, include the following: a hydro cushion cell barrier composed of an array ofliquid filled plastic cells operable such that upon impact, the liquid is ejected through orifices in the top of the cells at a controlled rate; a barrier formed by an array of nine to seventeen sand-filled frangible plastic barrels, which is characterized by its versatile applicability; a U-shaped tubular guardrail energy absorbing barrier that absorbs energy by means of the motion of supporting telescopic tubes such that upon impact, the impact forces are transmitted axially to arms, which contain many stainless steel torus elements that are squeezed between two cylindrical tubes; a barrier in the form of a vehicle arresting system that is composed of a steel entrapping net positioned across a roadway, and which is particularly applicable for use in proximity to locations such as road dead ends, fery landings, highway medians at bridge overpasses, etc.; a lightweight cellular concrete crash cushion barrier constructed of easily frangible vermiculite concrete with vertical voids wherein the vertical voids contribute to the controlled crushing characteristics of the barrier; honeycomb cells that are filled with polyurethane foam; in other instances the honeycomb cells are themselves made of aluminum; for use primarily as part of a guardrail system, a barrier based on a fragmenting tube concept, which was originally developed for use in planned lunar landing modules, and in which energy is absorbed by forcing a thick walled aluminum tube over a flared die, resulting in the shredding of the tube into small segments; and lastly, an energy absorbing barrier particularly applicable for use as part of a guardrail system and in which thick walled steel rings are utilized.
Yet another example of a prior art form of stationary energy absorbing barrier, and one that has found favor with those who have a need for such systems, is that which forms the subject matter of U.S. Pat. No. 4,645,375, which issued on Feb. 24, 1987 to the same inventor as that of the present application and which is assigned to the same assignee as the present application. As described therein, the stationary energy absorbing barrier. which is operable for reducing the severity of vehicular collisions occasioned by an errant vehicle striking an immovable object including support means, impact attenuating means and protective means. The support means is located in juxtaposed relation to an immovable object and so as to lie between the immovable object and an oncoming errant vehicle. The impact attenuating means is positioned in supported relation on the support means and is selectively operative to entrap an errant vehicle striking the stationary energy absorbing barrier at a second location. The protective means is positioned in juxtaposed relation to the impact attenuating means and is operative to prevent the buildup of snow and ice on the other components that comprise the stationary energy absorbing barrier.
In summary, the favorable energy dissipation capabilities of laterally loaded metallic cylinders, i.e., "crash cushions", have led to their widespread employment in impact attenuation devices used in highway safety applications. These crash cushions have included both portable and stationary devices. In both systems, energy is dissipated by deforming mild steel cylinders inelastically to deformations approaching ninety (90) percent of their original outside diameters under high speed impacts, e.g., sixty (60) miles per hour (mph), with heavy vehicles, e.g., vehicles weighing 4500 pounds (lbs.). The portable system preferably is emplaced in slow-moving maintenance operations, e.g., line-striping, to provide protection for both the errant motorist and maintenance personnel. The stationary system known as the Connecticut Impact Attenuation System (CIAS), which forms the subject matter of the aforementioned U.S. Pat. No. 4,645,375, is composed of fourteen (14) mild steel cylinders of three (3) or four (4) foot diameters such that at its base the CIAS is approximately twelve (12) feet in width. All of the cylinders in the CIAS are four feet high, but the individual wall thicknesses vary from cylinder to cylinder. The CIAS is unique in that it will trap the errant vehicle when the vehicle impacts the CIAS on the side unless the area of the impact on the CIAS is so close to the back of the CIAS that significant energy dissipation and acceptable deceleration responses are unobtainable because of the proximity of the hazard. Only in this situation will the CIAS redirect the vehicle back into the traffic flow direction. In order to cope with this need for the CIAS to redirect the vehicle back into the traffic flow direction when a vehicle impacts the CIAS near the rear thereof, steel "tension" straps, which are ineffective under compressive loading, and "compression" pipes, which are ineffective in tension, are employed. This bracing structure that the CIAS embodies ensures that the CIAS will respond in a stiff manner when subjected to an oblique impact near the rear of the CIAS, providing the necessary lateral force to redirect the errant vehicle. On the other hand, the braced tubes of the CIAS retain their unstiffened responses when the cylinders of the CIAS are crushed by impacts away from the back of the CIAS. The CIAS is being employed in several states in the United States. It has been credited with saving lives and greatly reducing the severities of injuries associated with high speed accidents by reducing the deceleration levels of the occupants.
Notwithstanding the effectiveness that the CIAS has demonstrated in reducing the severities of injuries associated with high speed encounters between errant vehicles and immovable objects, a need has nevertheless been evidenced for a new and improved form of stationary impact attenuation system, and in particular a new and improved form of stationary impact attenuation system that would be at least as effective as the CIAS in reducing the severity of injuries occasioned by high speed encounters between errant vehicles and immovable objects, but unlike the CIAS would be capable of being employed at narrow hazard sites. Examples of such narrow hazard sites include the ends of edge-of-road and median barriers, bridge pillars, and center piers. In order to be capable of use in such narrow hazard sites, such a new and improved stationary impact attenuation system must not exceed approximately three (3) feet in width as contrasted to the CIAS which at its base is approximately twelve (12) feet in width. There are a number of characteristics, which it is desired that such a new and improved narrow stationary impact attenuation system should possess. Namely, such a narrow stationary impact attenuation system should be operative to trap the errant vehicle when struck headon by an errant vehicle weighing up to 4500 lbs. that is traveling at a speed of up to sixty (60) mph when the narrow stationary impact attenuation system is struck thereby. On the other hand, the narrow stationary impact attenuation system should be operative to redirect the errant vehicle into the traffic flow direction when the narrow stationary impact attenuation system is struck other than headon by an errant vehicle weighting up to 4500 lbs. that is traveling at a speed of up to sixty (60) mph when the narrow stationary impact attenuation system is struck thereby. In addition, the narrow stationary impact attenuation system should be capable of satisfying the applicable performance standards as outlined in NCHRP Report 230. Moreover, the narrow stationary impact attenuation system should be capable of being constructed from readily available materials, and should be inexpensive to repair after having been struck by an errant vehicle. Also, use of the narrow stationary impact attenuation system should not be unduly limited because of considerations of terrrain, etc. Finally, the narrow stationary impact attenuation system should be characterized by the fact that when struck by an errant vehicle there is no flying debris associated with the crash event.
It is, therefore, an object of the present invention to provide a new and improved form of stationary impact attenuation system operable to reduce the severity of vehicular collisions with immovable objects.
It is another object of the present invention to provide such a stationary impact attenuation system, which is particularly suited for employment as a stationary system at narrow hazard sites to afford protection to immovable objects from otherwise being struck by an errant vehicle.
A further object of the present invention is to provide such a narrow stationary impact attenuation system, which is operative when struck headon by an errant vehicle weighing up to 4500 lbs. and traveling at a speed of up to sixty (60) mph to entrap the errant vehicle striking the system.
A still further object of the present invention is to provide such a narrow stationary impact attenuation system, which is operative other than when struck headon by an errant vehicle weighing up to 4500 lbs. and traveling at a speed of up to sixty (60) mph to redirect the errant vehicle striking the system into the traffic flow direction.
Yet another object of the present invention is to provide such a narrow stationary impact attenuation system which is capable of satisfying the applicable impact performance standards as outlined in NCHRP Report 230.
Yet still another object of the present invention is to provide such a narrow stationary impact attenuation system, the use of which is not unduly limited because of considerations of terrain, etc.
Yet a further object of the present invention is to provide such a narrow stationary impact attenuation system which is characterized by the fact that when struck by an errant vehicle there is no flying debris associated with the crash event.
Yet a still further object is to provide such a narrow stationary impact attenuation system which is capable of being constructed of readily available materials, and is inexpensive to repair after having been struck by an errant vehicle.